Mechanisms of BCR-ABL in the pathogenesis of chronic myelogenous leukaemia

Interaction analysis of RNA G-quadruplex with ligands and in situ imaging application

RNA G4, as an integral branch of G4 structure, possesses distinct interactions with ligands compared to the common DNA G4, thus the investigation of RNA G4/ligand interactions might be considered as a fresh breakthrough to improve the biosensing performance of G4/ligand system. In this study, we comparatively explored the structural and functional mechanisms of RNA G4 and DNA G4 in the interaction with ligands, hemin and thioflavin T (ThT), utilizing the classical PS2.M sequence as a model. We found that although the catalytic performance of RNA G4/hemin system was lower than DNA G4/hemin, RNA G4/ThT fluorescence system exhibited a significant improvement (2∼3-fold) compared to DNA G4/ThT, and adenine modification could further enhance the signaling. Further, by exploring the interaction between RNA G4 and ThT, we deemed that RNA G4 and ThT were stacked in a bimolecular mode compared to single-molecule binding of DNA G4/ThT, thus more strongly limiting the structural spin in ThT excited state. Further, RNA G4/ThT displayed higher environmental tolerance and lower ion dependence than DNA G4/ThT. Finally, we employed RNA G4/ThT as a highly sensitive label-free fluorescent signal output system for in situ imaging of isoforms BCR-ABL e13a2 and e14a2. Overall, this study successfully screened a high-performance RNA G4 biosensing system through systematic RNA G4/ligands interaction studies, which was expected to provide a promising reference for subsequent G4/ligand research.

Comparative analysis of BCR::ABL1 p210 mRNA transcript quantification and ratio to ABL1 control gene converted to the International Scale by chip digital PCR and droplet digital PCR for monitoring patients with chronic myeloid leukemia

OBJECTIVES

Chronic myeloid leukemia (CML) is characterized by the Philadelphia chromosome, leading to the BCR::ABL1 fusion gene and hyper-proliferation of granulocytes. Tyrosine kinase inhibitors (TKIs) are effective, and minimal residual disease (MRD) monitoring is crucial. Digital PCR platforms offer increased precision compared to quantitative PCR but lack comparative studies.

METHODS

Eighty CML patient samples were analyzed in parallel using digital droplet PCR (ddPCR) (QXDx™ BCR-ABL %IS Kit) and chip digital PCR (cdPCR) (Dr. PCR™ BCR-ABL1 Major IS Detection Kit).

RESULTS

Overall, qualitative and quantitative agreement was good. Sensitivity analysis showed positive percentage agreement and negative percentage agreement were both ≥90 %, and the quadratic weighted kappa index for molecular response (MR) level categorization was 0.94 (95 %CI 0.89, 0.98). MR levels subgroup analysis showed perfect categorical agreement on MR level at MR3 or above, while 35.4 % (17/48) of patient samples with MR4 or below showed discordant categorizations. Overall, Lin's concordance correlation coefficient (CCC) for the ratio of %BCR::ABL1/ABL1 converted to the International Scale (BCR::ABL1 IS) was almost perfect quantitative agreement (Lin's CCC=0.99). By subgroups of MR levels, Lin's CCC showed a quantitative agreement of BCR::ABL1 IS decreased as MR deepened.

CONCLUSIONS

Both cdPCR and ddPCR demonstrated comparable performance in detecting BCR::ABL1 transcripts with high concordance in MR3 level or above. Choosing between platforms may depend on cost, workflow, and sensitivity requirements.

Non-Receptor Tyrosine Kinases: Their Structure and Mechanistic Role in Tumor Progression and Resistance

Protein tyrosine kinases (PTKs) function as key molecules in the signaling pathways in addition to their impact as a therapeutic target for the treatment of many human diseases, including cancer. PTKs are characterized by their ability to phosphorylate serine, threonine, or tyrosine residues and can thereby rapidly and reversibly alter the function of their protein substrates in the form of significant changes in protein confirmation and affinity for their interaction with protein partners to drive cellular functions under normal and pathological conditions. PTKs are classified into two groups: one of which represents tyrosine kinases, while the other one includes the members of the serine/threonine kinases. The group of tyrosine kinases is subdivided into subgroups: one of them includes the member of receptor tyrosine kinases (RTKs), while the other subgroup includes the member of non-receptor tyrosine kinases (NRTKs). Both these kinase groups function as an "on" or "off" switch in many cellular functions. NRTKs are enzymes which are overexpressed and activated in many cancer types and regulate variable cellular functions in response to extracellular signaling-dependent mechanisms. NRTK-mediated different cellular functions are regulated by kinase-dependent and kinase-independent mechanisms either in the cytoplasm or in the nucleus. Thus, targeting NRTKs is of great interest to improve the treatment strategy of different tumor types. This review deals with the structure and mechanistic role of NRTKs in tumor progression and resistance and their importance as therapeutic targets in tumor therapy.

IL-1 in aging and pathologies of hematopoietic stem cells

ABSTRACT

Defense-oriented inflammatory reactivity supports survival at younger age but might contribute to health impairments in modern, aging societies. The interleukin-1 (IL-1) cytokines are highly conserved and regulated, pleiotropic mediators of inflammation, essential to respond adequately to infection and tissue damage but also with potential host damaging effects when left unresolved. In this review, we discuss how continuous low-level IL-1 signaling contributes to aging-associated hematopoietic stem and progenitor cell (HSPC) functional impairments and how this inflammatory selective pressure acts as a driver of more profound hematological alterations, such as clonal hematopoiesis of indeterminate potential, and to overt HSPC diseases, like myeloproliferative and myelodysplastic neoplasia as well as acute myeloid leukemia. Based on this, we outline how IL-1 pathway inhibition might be used to prevent or treat inflammaging-associated HSPC pathologies.

Gallic Acid Enhances the Efficacy of BCR::ABL1 Tyrosine Kinase Inhibitors in Chronic Myeloid Leukemia through Inhibition of Mitochondrial Respiration and Modulation of Oncogenic Signaling Pathways

While BCR::ABL1 tyrosine kinase inhibitors have transformed the treatment paradigm for chronic myeloid leukemia (CML), disease progression and treatment resistance due to BCR::ABL1-dependent and BCR::ABL1-independent mechanisms remain a therapeutic challenge. Natural compounds derived from plants have significantly contributed to cancer pharmacotherapy. This study investigated the efficacy of an active component of Leea indica, a local medicinal plant, in CML. Using high-performance liquid chromatography-electrospray ionization-mass spectrometry, a chemical constituent from L. indica extract was isolated and identified as gallic acid. Commercially obtained gallic acid was used as a chemical standard. Gallic acid from L. indica inhibited proliferation and induced apoptosis in CML cell lines, as did the chemical standard. Furthermore, gallic acid induced apoptosis and decreased the colony formation of primary CML CD34+ cells. The combination of isolated gallic acid or its chemical standard with BCR::ABL1 tyrosine kinase inhibitors resulted in a significantly greater inhibition of colony formation and cell growth compared to a single drug alone. Mechanistically, CML cells treated with gallic acid exhibited the disruption of multiple oncogenic pathways including ERK/MAPK, FLT3 and JAK/STAT, as well as impaired mitochondrial respiration. Rescue studies showed that gallic acid is significantly less effective in inducing apoptosis in mitochondrial respiration-deficient ρ0 cells compared to wildtype cells, suggesting that the action of gallic acid is largely through the inhibition of mitochondrial respiration. Our findings highlight the therapeutic potential of L. indica in CML and suggest that gallic acid may be a promising lead chemical constituent for further development for CML treatment.

Glutathione determines chronic myeloid leukemia vulnerability to an inhibitor of CMPK and TMPK

Bcr-Abl transformation leads to chronic myeloid leukemia (CML). The acquirement of T315I mutation causes tyrosine kinase inhibitors (TKI) resistance. This study develops a compound, JMF4073, inhibiting thymidylate (TMP) and cytidylate (CMP) kinases, aiming for a new therapy against TKI-resistant CML. In vitro and in vivo treatment of JMF4073 eliminates WT-Bcr-Abl-32D CML cells. However, T315I-Bcr-Abl-32D cells are less vulnerable to JMF4073. Evidence is presented that ATF4-mediated upregulation of GSH causes T315I-Bcr-Abl-32D cells to be less sensitive to JMF4073. Reducing GSH biosynthesis generates replication stress in T315I-Bcr-Abl-32D cells that require dTTP/dCTP synthesis for survival, thus enabling JMF4073 susceptibility. It further shows that the levels of ATF4 and GSH in several human CML blast-crisis cell lines are inversely correlated with JMF4073 sensitivity, and the combinatory treatment of JMF4073 with GSH reducing agent leads to synthetic lethality in these CML blast-crisis lines. Altogether, the investigation indicates an alternative option in CML therapy.

A case of Ph+ acute lymphoblastic leukemia and EGFR mutant lung adenocarcinoma synchronous overlap: may one TKI drug solve two diseases?

BACKGROUND

Philadelphia chromosome positive (Ph+) acute lymphoblastic leukemia (ALL) refers to ALL patients with t(9;22) cytogenetic abnormalities, accounting for about 25% of ALL. Lung adenocarcinoma (LUAD) is the most common pathological type of non-small-cell lung cancer, which has a frequency of approximately 45% cases with mutations in EGFR. Both Ph+ ALL and EGFR mutant LUAD are involved in the pathogenesis of the abnormal activation of the tyrosine kinase pathway. Although the second primary hematological malignancy after the treatment of solid tumors is common in clinics, the synchronous multiple primary malignant tumors of hematological malignancy overlap solid tumors are uncommon, even both tumors involved in the pathogenesis of the abnormal activation of the tyrosine kinase pathway are extremely rare.

CASE PRESENTATION

An 84-year-old man with fatigue and dizziness was diagnosed with Ph+ ALL. Meanwhile, a chest CT indicated a space-occupying lesions, characterized by the presence of void, in the right lower lope with the enlargement of mediastinal lymph node and right pleural effusion. After a few weeks, the patient was diagnosed with LUAD with EGFR exon 19 mutation. Both tyrosine kinase inhibitors (TKI) (Flumatinib) and EGFR-TKI (Oxertinib) was used for the patients, and finally have controlled both diseases.

CONCLUSION

As far as we know, we for the first time reported a case of Ph+ ALL and EGFR mutant LUAD synchronous overlap, of which pathogenesis is related to abnormal tyrosine kinase activation. This patient was successfully treated with two different TKIs without serious adverse events.

Inferring kinase activity from phosphoproteomic data: Tool comparison and recent applications

Aberrant cellular signaling pathways are a hallmark of cancer and other diseases. One of the most important signaling mechanisms involves protein phosphorylation/dephosphorylation. Protein phosphorylation is catalyzed by protein kinases, and over 530 protein kinases have been identified in the human genome. Aberrant kinase activity is one of the drivers of tumorigenesis and cancer progression and results in altered phosphorylation abundance of downstream substrates. Upstream kinase activity can be inferred from the global collection of phosphorylated substrates. Mass spectrometry-based phosphoproteomic experiments nowadays routinely allow identification and quantitation of >10k phosphosites per biological sample. This substrate phosphorylation footprint can be used to infer upstream kinase activities using tools like Kinase Substrate Enrichment Analysis (KSEA), Posttranslational Modification Substrate Enrichment Analysis (PTM-SEA), and Integrative Inferred Kinase Activity Analysis (INKA). Since the topic of kinase activity inference is very active with many new approaches reported in the past 3 years, we would like to give an overview of the field. In this review, an inventory of kinase activity inference tools, their underlying algorithms, statistical frameworks, kinase-substrate databases, and user-friendliness is presented. The most widely-used tools are compared in-depth. Subsequently, recent applications of the tools are described focusing on clinical tissues and hematological samples. Two main application areas for kinase activity inference tools can be discerned. (1) Maximal biological insights can be obtained from large data sets with group comparisons using multiple complementary tools (e.g., PTM-SEA and KSEA or INKA). (2) In the oncology context where personalized treatment requires analysis of single samples, INKA for example, has emerged as tool that can prioritize actionable kinases for targeted inhibition.

TIF1β activates leukemic transcriptional program in HSCs and promotes BCR::ABL1-induced myeloid leukemia

TIF1β/KAP1/TRIM28, a chromatin modulator, both represses and activates the transcription of genes in normal and malignant cells. Analyses of datasets on leukemia patients revealed that the expression level of TIF1β was increased in patients with chronic myeloid leukemia at the blast crisis and acute myeloid leukemia. We generated a BCR::ABL1 conditional knock-in (KI) mouse model, which developed aggressive myeloid leukemia, and demonstrated that the deletion of the Tif1β gene inhibited the progression of myeloid leukemia and showed longer survival than that in BCR::ABL1 KI mice, suggesting that Tif1β drove the progression of BCR::ABL1-induced leukemia. In addition, the deletion of Tif1β sensitized BCR::ABL1 KI leukemic cells to dasatinib. The deletion of Tif1β decreased the expression levels of TIF1β-target genes and chromatin accessibility peaks enriched with the Fosl1-binding motif in BCR::ABL1 KI stem cells. TIF1β directly bound to the promoters of proliferation genes, such as FOSL1, in human BCR::ABL1 cells, in which TIF1β and FOSL1 bound to adjacent regions of chromatin. Since the expression of Fosl1 was critical for the enhanced growth of BCR::ABL1 KI cells, Tif1β and Fosl1 interacted to activate the leukemic transcriptional program in and cellular function of BCR::ABL1 KI stem cells and drove the progression of myeloid leukemia.

PROteolysis-Targeting Chimeras (PROTACs) in leukemia: overview and future perspectives

Leukemia is a heterogeneous group of life-threatening malignant disorders of the hematopoietic system. Immunotherapy, radiotherapy, stem cell transplantation, targeted therapy, and chemotherapy are among the approved leukemia treatments. Unfortunately, therapeutic resistance, side effects, relapses, and long-term sequelae occur in a significant proportion of patients and severely compromise the treatment efficacy. The development of novel approaches to improve outcomes is therefore an unmet need. Recently, novel leukemia drug discovery strategies, including targeted protein degradation, have shown potential to advance the field of personalized medicine for leukemia patients. Specifically, PROteolysis-TArgeting Chimeras (PROTACs) are revolutionary compounds that allow the selective degradation of a protein by the ubiquitin-proteasome system. Developed against a wide range of cancer targets, they show promising potential in overcoming many of the drawbacks associated with conventional therapies. Following the exponential growth of antileukemic PROTACs, this article reviews PROTAC-mediated degradation of leukemia-associated targets. Chemical structures, in vitro and in vivo activities, pharmacokinetics, pharmacodynamics, and clinical trials of PROTACs are critically discussed. Furthermore, advantages, challenges, and future perspectives of PROTACs in leukemia are covered, in order to understand the potential that these novel compounds may have as future drugs for leukemia treatment.

Omics-based molecular classifications empowering in precision oncology

BACKGROUND

In the past decades, cancer enigmatical heterogeneity at distinct expression levels could interpret disparities in therapeutic response and prognosis. It built hindrances to precision medicine, a tactic to tailor customized treatment informed by the tumors' molecular profile. Single-omics analysis dissected the biological features associated with carcinogenesis to some extent but still failed to revolutionize cancer treatment as expected. Integrated omics analysis incorporated tumor biological networks from diverse layers and deciphered a holistic overview of cancer behaviors, yielding precise molecular classification to facilitate the evolution and refinement of precision medicine.

CONCLUSION

This review outlined the biomarkers at multiple expression layers to tutor molecular classification and pinpoint tumor diagnosis, and explored the paradigm shift in precision therapy: from single- to multi-omics-based subtyping to optimize therapeutic regimens. Ultimately, we firmly believe that by parsing molecular characteristics, omics-based typing will be a powerful assistant for precision oncology.

New Inhibitors of Bcr-Abl Based on 2,6,9-Trisubstituted Purine Scaffold Elicit Cytotoxicity in Chronic Myeloid Leukemia-Derived Cell Lines Sensitive and Resistant to TKIs

Bcr-Abl is an oncoprotein with aberrant tyrosine kinase activity involved in the progression of chronic myeloid leukemia (CML) and has been targeted by inhibitors such as imatinib and nilotinib. However, despite their efficacy in the treatment of CML, a mechanism of resistance to these drugs associated with mutations in the kinase region has emerged. Therefore, in this work, we report the synthesis of 14 new 2,6,9-trisubstituted purines designed from our previous Bcr-Abl inhibitors. Here, we highlight 11b, which showed higher potency against Bcr-Abl (IC50 = 0.015 μM) than imatinib and nilotinib and exerted the most potent antiproliferative properties on three CML cells harboring the Bcr-Abl rearrangement (GI50 = 0.7-1.3 μM). In addition, these purines were able to inhibit the growth of KCL22 cell lines expressing Bcr-AblT315I, Bcr-AblE255K, and Bcr-AblY253H point mutants in micromolar concentrations. Imatinib and nilotinib were ineffective in inhibiting the growth of KCL22 cells expressing Bcr-AblT315I (GI50 > 20 μM) compared to 11b-f (GI50 = 6.4-11.5 μM). Molecular docking studies explained the structure-activity relationship of these purines in Bcr-AblWT and Bcr-AblT315I. Finally, cell cycle cytometry assays and immunodetection showed that 11b arrested the cells in G1 phase, and that 11b downregulated the protein levels downstream of Bcr-Abl in these cells.

Precision Medicine in Veterinary Science

Precision medicine focuses on the clinical management of the individual patient, not on population-based findings. Successes from human precision medicine inform veterinary oncology. Early evidence of success for canines shows how precision medicine can be integrated into practice. Decreasing genomic profiling costs will allow increased utilization and subsequent improvement of knowledge base from which to make better informed decisions. Utility of precision medicine in canine oncology will only increase for improved cancer characterization, enhanced therapy selection, and overall more successful management of canine cancer. As such, practitioners are called to interpret and leverage precision medicine reports for their patients.

MOSAIC enables in situ saturation mutagenesis of genes and CRISPR prime editing guide RNA optimization in human cells

CRISPR prime editing offers unprecedented versatility and precision for the installation of genetic edits in situ . Here we describe the development and characterization of the Multiplexing Of Site-specific Alterations for In situ Characterization ( MOSAIC ) method, which leverages a non-viral PCR-based prime editing method to enable rapid installation of thousands of defined edits in pooled fashion. We show that MOSAIC can be applied to perform in situ saturation mutagenesis screens of: (1) the BCR-ABL1 fusion gene, successfully identifying known and potentially new imatinib drug-resistance variants; and (2) the IRF1 untranslated region (UTR), re-confirming non-coding regulatory elements involved in transcriptional initiation. Furthermore, we deployed MOSAIC to enable high-throughput, pooled screening of hundreds of systematically designed prime editing guide RNA ( pegRNA ) constructs for a large series of different genomic loci. This rapid screening of >18,000 pegRNA designs identified optimized pegRNAs for 89 different genomic target modifications and revealed the lack of simple predictive rules for pegRNA design, reinforcing the need for experimental optimization now greatly simplified and enabled by MOSAIC. We envision that MOSAIC will accelerate and facilitate the application of CRISPR prime editing for a wide range of high-throughput screens in human and other cell systems.

Mutation analysis of BCR-ABL1 kinase domain in chronic myeloid leukemia patients with tyrosine kinase inhibitors resistance: a Malaysian cohort study

OBJECTIVE

Mutational analysis of BCR::ABL1 kinase domain (KD) is a crucial component of clinical decision algorithms for chronic myeloid leukemia (CML) patients with failure or warning responses to tyrosine kinase inhibitor (TKI) therapy. This study aimed to detect BCR::ABL1 KD mutations in CML patients with treatment resistance and assess the concordance between NGS (next generation sequencing) and Sanger sequencing (SS) in detecting these mutations.

RESULTS

In total, 12 different BCR::ABL1 KD mutations were identified by SS in 22.6% (19/84) of patients who were resistant to TKI treatment. Interestingly, NGS analysis of the same patient group revealed an additional four different BCR::ABL1 KD mutations in 27.4% (23/84) of patients. These mutations are M244V, A344V, E355A, and E459K with variant read frequency below 15%. No mutation was detected in 18 patients with optimal response to TKI therapy. Resistance to TKIs is associated with the acquisition of additional mutations in BCR::ABL1 KD after treatment with TKIs. Additionally, the use of NGS is advised for accurately determining the mutation status of BCR::ABL1 KD, particularly in cases where the allele frequency is low, and for identifying mutations across multiple exons simultaneously. Therefore, the utilization of NGS as a diagnostic platform for this test is very promising to guide therapeutic decision-making.

Oxidative Stress and Chronic Myeloid Leukemia: A Balance between ROS-Mediated Pro- and Anti-Apoptotic Effects of Tyrosine Kinase Inhibitors

The balanced reciprocal translocation t (9; 22) (q34; q11) and the BCR-ABL fusion gene, which produce p210 bcr-abl protein production with high tyrosine kinase activity, are characteristics of chronic myeloid leukemia, a myeloproliferative neoplasm. This aberrant protein affects several signaling pathways connected to both apoptosis and cell proliferation. It has been demonstrated that tyrosine kinase inhibitor treatment in chronic myeloid leukemia acts by inducing oxidative stress and, depending on its level, can activate signaling pathways responsible for either apoptosis or survival in leukemic cells. Additionally, oxidative stress and reactive oxygen species generation also mediate apoptosis through genomic activation. Furthermore, it was shown that oxidative stress has a role in both BCR-ABL-independent and BCR-ABL-dependent resistance pathways to tyrosine kinases, while patients with chronic myeloid leukemia were found to have a significantly reduced antioxidant level. The ideal environment for tyrosine kinase inhibitor therapy is produced by a favorable oxidative status. We discuss the latest studies that aim to manipulate the redox system to alter the apoptosis of cancerous cells.

Annual review of PROTAC degraders as anticancer agents in 2022

Following nearly two decades of development, significant advancements have been achieved in PROTAC technology. As of the end of 2022, more than 20 drugs have entered clinical trials, with ARV-471 targeting estrogen receptor (ER) showing remarkable progress by entering phase III clinical studies. In 2022, significant progress has been made on multiple targets. The first reversible covalent degrader designed to target the KRASG12C mutant protein, based on cyclopropionamide, has been reported. Additionally, the activity HDCA1 degrader surpassed submicromolar levels during the same year. A novel FEM1B covalent ligand called EN106 was also discovered, expanding the range of available ligands. Furthermore, the first PROTAC drug targeting SOS1 was reported. Additionally, the first-in-class degraders that specifically target BRD4 isoforms (BRD4 L and BRD4 S) have recently been reported, providing a valuable tool for further investigating the biological functions of these isoforms. Lastly, a breakthrough was also achieved with the first degrader targeting both CDK9 and Cyclin T1. In this review, we aimed to update the PROTAC degraders as potential anticancer agents covering articles published in 2022. The design strategies, degradation effects, and anticancer activities were highlighted, which might provide an updated sight to develop novel PROTAC degraders with great potential as anticancer agents as well as favorable drug-like properties.

Inhibition of mitochondrial folate metabolism drives differentiation through mTORC1 mediated purine sensing

Supporting cell proliferation through nucleotide biosynthesis is an essential requirement for cancer cells. Hence, inhibition of folate-mediated one carbon (1C) metabolism, which is required for nucleotide synthesis, has been successfully exploited in anti-cancer therapy. Here, we reveal that mitochondrial folate metabolism is upregulated in patient-derived leukaemic stem cells (LSCs). We demonstrate that inhibition of mitochondrial 1C metabolism through impairment of de novo purine synthesis has a cytostatic effect on chronic myeloid leukaemia (CML) cells. Consequently, changes in purine nucleotide levels lead to activation of AMPK signalling and suppression of mTORC1 activity. Notably, suppression of mitochondrial 1C metabolism increases expression of erythroid differentiation markers. Moreover, we find that increased differentiation occurs independently of AMPK signalling and can be reversed through reconstitution of purine levels and reactivation of mTORC1. Of clinical relevance, we identify that combination of 1C metabolism inhibition with imatinib, a frontline treatment for CML patients, decreases the number of therapy-resistant CML LSCs in a patient-derived xenograft model. Our results highlight a role for folate metabolism and purine sensing in stem cell fate decisions and leukaemogenesis.

The dark side of stemness - the role of hematopoietic stem cells in development of blood malignancies

Hematopoietic stem cells (HSCs) produce all blood cells throughout the life of the organism. However, the high self-renewal and longevity of HSCs predispose them to accumulate mutations. The acquired mutations drive preleukemic clonal hematopoiesis, which is frequent among elderly people. The preleukemic state, although often asymptomatic, increases the risk of blood cancers. Nevertheless, the direct role of preleukemic HSCs is well-evidenced in adult myeloid leukemia (AML), while their contribution to other hematopoietic malignancies remains less understood. Here, we review the evidence supporting the role of preleukemic HSCs in different types of blood cancers, as well as present the alternative models of malignant evolution. Finally, we discuss the clinical importance of preleukemic HSCs in choosing the therapeutic strategies and provide the perspective on further studies on biology of preleukemic HSCs.

A case report of a truncated ABL1 mutation in 2 cases with Philadelphia chromosome-positive B cell precursor acute lymphoblastic leukemia

Acquired point mutations in the ABL1 gene are widely recognized as a cause of Philadelphia chromosome-positive B cell precursor acute lymphoblastic leukemia (Ph+ B-ALL) that is resistant to tyrosine kinase inhibitors, whereas there are few reports about other types of the ABL1 mutation. Here, we report 2 cases of Ph+ B-ALL gaining a partial deletion type mutation of the ABL1 gene (Δ184-274 mutation), which resulted in truncation of the ABL1 molecule and loss of kinase activity. In both cases, the disease was refractory to multiple agents in the recurrent phase after allogeneic hematopoietic cell transplantation. This is a case report of a truncated ABL1 mutation in 2 patients with Ph+ B-ALL.

JC-010a, a novel selective SHP2 allosteric inhibitor, overcomes RTK/non-RTK-mediated drug resistance in multiple oncogene-addicted cancers

Src homology 2 domain-containing phosphatase (SHP2) is a non-receptor protein phosphatase that transduces signals from upstream receptor tyrosine kinases (RTKs)/non-RTKs to Ras/MAPK pathway. Accumulating studies indicated that SHP2 is a critical mediator of resistance to current targeted therapies in multiple cancers. Here, we reported a novel SHP2 allosteric inhibitor JC-010a, which was highly selective to SHP2 and bound at the "tunnel" allosteric site of SHP2. The effect of JC-010a on combating RTK/non-RTK or MAPK inhibitors-induced acquired resistance was explored. Our study demonstrated that JC-010a monotherapy significantly inhibited the proliferation of cancer cells with different oncogenic drivers via inhibiting signaling through SHP2. Importantly, JC-010a abolished acquired resistance induced by targeted therapies: in KRAS-mutant cancers, JC-010a abrogated selumetinib-induced adaptive resistance mediated by RTK/SHP2; in BCR-ABL-driven leukemia cells, we demonstrated JC-010a inhibited BCR-ABL T315I mutation-mediated imatinib resistance and proposed a novel mechanism of JC-010a involving the disrupted co-interaction of SHP2, BCR-ABL, and Hsp90; in non-small cell lung cancer (NSCLC) cells, JC-010a inhibited both EGFR T790M/C797S mutation and alternate RTK-driven resistance to gefitinib or osimertinib; importantly, we first proposed a novel potential therapeutic strategy for RET-rearranged cancer, we confirmed that JC-010a monotherapy inhibited cell resistance to BLU-667, and JC-010a/BLU-667 combination prolonged anticancer response both in vivo and in vitro cancer models by inhibiting the alternate MET activation-induced RAS/MAPK reactivation, thereby promoting cancer cell apoptosis. These findings suggested that JC-010a was a novel selective SHP2 allosteric inhibitor, and combing JC-010a with current targeted therapy agents provided a promising therapeutic approach for clinical resistant cancers.

Extracellular vesicles in the Chronic Myeloid Leukemia scenario: an update about the shuttling of disease markers and therapeutic molecules

Extracellular vesicles (EVs) are various sets of cell-derived membranous structures containing lipids, nucleic acids, and proteins secreted by both eukaryotic and prokaryotic cells. It is now well recognized that EVs are key intercellular communication mediators, allowing the functional transfer of bioactive chemicals from one cell to another in both healthy and pathological pathways. It is evident that the condition of the producer cells heavily influences the composition of EVs. Hence, phenotypic changes in the parent cells are mirrored in the design of the secreted EVs. As a result, EVs have been investigated for a wide range of medicinal and diagnostic uses in different hematological diseases. EVs have only recently been studied in the context of Chronic Myeloid Leukemia (CML), a blood malignancy defined by the chromosomal rearrangement t(9;22) and the fusion gene BCR-ABL1. The findings range from the impact on pathogenesis to the possible use of EVs as medicinal chemical carriers. This review aims to provide for the first time an update on our understanding of EVs as carriers of CML biomarkers for minimal residual disease monitoring, therapy response, and its management, as well as the limited reports on the use of EVs as therapeutic shuttles for innovative treatment approaches.

Interleukin-1 receptor accessory protein (IL-1RAP): A magic bullet candidate for immunotherapy of human malignancies

IL-1, plays a role in some pathological inflammatory conditions. This pro-inflammatory cytokine also has a crucial role in tumorigenesis and immune responses in the tumor microenvironment (TME). IL-1 receptor accessory protein (IL-1RAP), combined with IL-1 receptor-1, provides a functional complex for binding and signaling. In addition to the direct role of IL-1, some studies demonstrated that IL1-RAP has essential roles in the progression, angiogenesis, and metastasis of solid tumors such as gastrointestinal tumors, lung carcinoma, glioma, breast and cervical cancers. This molecule also interacts with FLT-3 and c-Kit tyrosine kinases and is involved in the pathogenesis of hematological malignancies such as acute myeloid lymphoma. Additionally, IL-1RAP interacts with solute carrier family 3 member 2 (SLC3A2) and thereby increasing the resistance to anoikis and metastasis in Ewing sarcoma. This review summarizes the role of IL-1RAP in different types of cancers and discusses its targeting as a novel therapeutic approach for malignancies.

Protein kinases: drug targets for immunological disorders

Protein kinases play a major role in cellular activation processes, including signal transduction by diverse immunoreceptors. Given their roles in cell growth and death and in the production of inflammatory mediators, targeting kinases has proven to be an effective treatment strategy, initially as anticancer therapies, but shortly thereafter in immune-mediated diseases. Herein, we provide an overview of the status of small molecule inhibitors specifically generated to target protein kinases relevant to immune cell function, with an emphasis on those approved for the treatment of immune-mediated diseases. The development of inhibitors of Janus kinases that target cytokine receptor signalling has been a particularly active area, with Janus kinase inhibitors being approved for the treatment of multiple autoimmune and allergic diseases as well as COVID-19. In addition, TEC family kinase inhibitors (including Bruton's tyrosine kinase inhibitors) targeting antigen receptor signalling have been approved for haematological malignancies and graft versus host disease. This experience provides multiple important lessons regarding the importance (or not) of selectivity and the limits to which genetic information informs efficacy and safety. Many new agents are being generated, along with new approaches for targeting kinases.

High BCR::ABL1 Expression Defines CD34+ Cells with Significant Alterations in Signal Transduction, Short-Proliferative Potential and Self-Renewal Ability

Purpose

Chronic Myeloid Leukemia (CML) is a clonal disorder of the hematopoietic stem cell caused by expression of the BCR::ABL1 oncoprotein. High BCR::ABL1 levels have been associated to proliferative advantage of leukemic cells, blast crisis progression and tyrosine kinase inhibitors (TKIs) inefficacy. We have previously shown that high BCR::ABL1/GUSIS transcripts measured at diagnosis are associated with inferior responses to standard dose Imatinib (IM). However, the mechanisms underlying the higher rates of disease progression and development of TKIs resistance dependent on elevated BCR::ABL1 levels remain unclear.

Methods

Leukemic cells were collected from CML patients showing, at diagnosis, high or low BCR::ABL1/GUSIS. BCR::ABL1 expression levels were measured using real-time PCR. Short-term culture and long-term culture-initiating cells assays were employed to investigate the role of BCR::ABL1 gene-expression levels on proliferation, clonogenicity, signal transduction, TKIs responsiveness and self-renewal ability. Cell division was performed by carboxyfluorescein-succinimidyl ester (CFSE) assay.

Results

We found that BCR::ABL1 oncogene expression levels correlate in both PMNs and CD34+ cells. Furthermore, high oncogene levels increased both proliferation and anti-apoptotic signaling via ERK and AKT phosphorylation. Moreover, high BCR::ABL1 expression reduced the clonogenicity of leukemic CD34+ cells and increased their sensitivity to high doses IM but not to those of dasatinib. Furthermore, we observed that high BCR::ABL1 levels are associated with a reduced self-renewal of primitive leukemic cells and, also, that these cells showed comparable TKIs responsiveness with cells expressing lower BCR::ABL1 levels. Interestingly, we found a direct correlation between high BCR::ABL1 levels and reduced number of quiescent leukemic cells caused by increasing their cycling.

Conclusion

Higher BCR::ABL1 levels improving the proliferation, anti-apoptotic signaling and reducing self-renewal properties cause an increased expansion of leukemic clone.

Asymmetric Hairpins DNA Encapsulated Silver Nanoclusters for In Situ Fluorescence Imaging of Fusion Gene Isoforms in Bone Marrow

Rapid and accurate imaging of the BCR/ABL fusion gene isoforms (e.g., e13a2, e14a2 and co-expression type) of chronic myeloid leukemia (CML) is of vital importance to first-line drug selection, but there is no assay that meets clinical needs (e.g., clinical kits > 18 h without isoforms information). Herein, an in situ imaging platform is developed for the rapid and accurate detection of CML fusion gene isoforms using asymmetric sequence-enhanced hairpins DNA encapsulated silver nanoclusters (ADHA) and catalyzed hairpin assembly (CHA). The specific detection of e13a2 and e14a2 fusion gene isoforms with detection limits of 19.2 am (11.558 copies µL-1 ) and 32.56 am (19.601 copies µL-1 ) in one-pot is achieved. The feasibility of the developed assay for real-world applications are demonstrated by one-step fluorescence imaging (40 min) of e13a2, e14a2 and co-expression type in bone marrow quantitatively (International Standard: 15.66%-168.878%) and further validated by cDNA-sequencing. This work suggests that the developed imaging platform holds great potential for rapid identification of the fusion gene isoforms and isoform related treatment monitoring.

Defining the condensate landscape of fusion oncoproteins

Fusion oncoproteins (FOs) arise from chromosomal translocations in ~17% of cancers and are often oncogenic drivers. Although some FOs can promote oncogenesis by undergoing liquid-liquid phase separation (LLPS) to form aberrant biomolecular condensates, the generality of this phenomenon is unknown. We explored this question by testing 166 FOs in HeLa cells and found that 58% formed condensates. The condensate-forming FOs displayed physicochemical features distinct from those of condensate-negative FOs and segregated into distinct feature-based groups that aligned with their sub-cellular localization and biological function. Using Machine Learning, we developed a predictor of FO condensation behavior, and discovered that 67% of ~3000 additional FOs likely form condensates, with 35% of those predicted to function by altering gene expression. 47% of the predicted condensate-negative FOs were associated with cell signaling functions, suggesting a functional dichotomy between condensate-positive and -negative FOs. Our Datasets and reagents are rich resources to interrogate FO condensation in the future.

Effect of asciminib and vitamin K2 on Abelson tyrosine-kinase-inhibitor-resistant chronic myelogenous leukemia cells

BACKGROUND

Abelson (ABL) tyrosine kinase inhibitors (TKIs) are effective against chronic myeloid leukemia (CML); however, many patients develop resistance during ABL TKI therapy. Vitamin K2 (VK2) is a crucial fat-soluble vitamin used to activate hepatic coagulation factors and treat osteoporosis. Although VK2 has demonstrated impressive anticancer activity in various cancer cell lines, it is not known whether VK2 enhances the effects of asciminib, which specifically targets the ABL myristoyl pocket (STAMP) inhibitor.

METHOD

In this work, we investigated whether VK2 contributed to the development of CML cell lines. We also investigated the efficacy of asciminib and VK2 by using K562, ponatinib-resistant K562 (K562 PR), Ba/F3 BCR-ABL, and T315I point mutant Ba/F3 (Ba/F3 T315I) cells.

RESULTS

Based on data from the Gene Expression Omnibus (GEO) database, gamma-glutamyl carboxylase (GGCX) and vitamin K epoxide reductase complex subunit 1 (VKORC1) were elevated in imatinib-resistant patients (GSE130404). UBIA Prenyltransferase Domain Containing 1 (UBIAD1) was decreased, and K562 PR cells were resistant to ponatinib. In contrast, asciminib inhibited CML cells and ponatinib resistance in a dose-dependent manner. CML cells were suppressed by VK2. Caspase 3/7 activity was also elevated, as was cellular cytotoxicity. Asciminib plus VK2 therapy induced a significantly higher level of cytotoxicity than use of each drug alone. Asciminib and VK2 therapy altered the mitochondrial membrane potential.

CONCLUSIONS

Asciminib and VK2 are suggested as a novel treatment for ABL-TKI-resistant cells since they increase treatment efficacy. Additionally, this treatment option has intriguing clinical relevance for patients who are resistant to ABL TKIs.

Histone demethylase PHF8 facilitates the development of chronic myeloid leukaemia by directly targeting BCR::ABL1

Although tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of chronic myeloid leukaemia (CML), TKI resistance remains a major challenge. Here, we demonstrated that plant homeodomain finger protein 8 (PHF8), a histone demethylase was aberrantly enriched in CML samples compared to healthy controls. PHF8 inhibited CML cell differentiation and promoted CML cell proliferation. Furthermore, the proliferation-inhibited function of PHF8-knockdown have stronger effect on imatinib mesylate (IM)-resistant CML cells. Mechanistically, we identified that PHF8 as a transcriptional modulator interacted with the promoter of the BCR::ABL1 fusion gene and alters the methylation levels of H3K9me1, H3K9me2 and H3K27me1, thereby promoting BCR::ABL1 transcription. Overall, our study suggests that targeting PHF8, which directly regulates BCR::ABL1 expression, is a useful therapeutic approach for CML.

The Importance of the Pyrazole Scaffold in the Design of Protein Kinases Inhibitors as Targeted Anticancer Therapies

The altered activation or overexpression of protein kinases (PKs) is a major subject of research in oncology and their inhibition using small molecules, protein kinases inhibitors (PKI) is the best available option for the cure of cancer. The pyrazole ring is extensively employed in the field of medicinal chemistry and drug development strategies, playing a vital role as a fundamental framework in the structure of various PKIs. This scaffold holds major importance and is considered a privileged structure based on its synthetic accessibility, drug-like properties, and its versatile bioisosteric replacement function. It has proven to play a key role in many PKI, such as the inhibitors of Akt, Aurora kinases, MAPK, B-raf, JAK, Bcr-Abl, c-Met, PDGFR, FGFRT, and RET. Of the 74 small molecule PKI approved by the US FDA, 8 contain a pyrazole ring: Avapritinib, Asciminib, Crizotinib, Encorafenib, Erdafitinib, Pralsetinib, Pirtobrutinib, and Ruxolitinib. The focus of this review is on the importance of the unfused pyrazole ring within the clinically tested PKI and on the additional required elements of their chemical structures. Related important pyrazole fused scaffolds like indazole, pyrrolo[1,2-b]pyrazole, pyrazolo[4,3-b]pyridine, pyrazolo[1,5-a]pyrimidine, or pyrazolo[3,4-d]pyrimidine are beyond the subject of this work.

De Novo Linear Phosphorylation Site Motifs for BCR-ABL Kinase Revealed by Phospho-Proteomics in Yeast

BCR-ABL is the oncogenic fusion product of tyrosine kinase ABL1 and a highly frequent driver of acute lymphocytic leukemia (ALL) and chronic myeloid leukemia (CML). The kinase activity of BCR-ABL is strongly elevated; however, changes of substrate specificity in comparison to wild-type ABL1 kinase are less well characterized. Here, we heterologously expressed full-length BCR-ABL kinases in yeast. We exploited the proteome of living yeast as an in vivo phospho-tyrosine substrate for assaying human kinase specificity. Phospho-proteomic analysis of ABL1 and BCR-ABL isoforms p190 and p210 yielded a high-confidence data set of 1127 phospho-tyrosine sites on 821 yeast proteins. We used this data set to generate linear phosphorylation site motifs for ABL1 and the oncogenic ABL1 fusion proteins. The oncogenic kinases yielded a substantially different linear motif when compared to ABL1. Kinase set enrichment analysis with human pY-sites that have high linear motif scores well-recalled BCR-ABL driven cancer cell lines from human phospho-proteome data sets.

Targeted in silico characterization of fusion transcripts in tumor and normal tissues via FusionInspector

Here, we present FusionInspector for in silico characterization and interpretation of candidate fusion transcripts from RNA sequencing (RNA-seq) and exploration of their sequence and expression characteristics. We applied FusionInspector to thousands of tumor and normal transcriptomes and identified statistical and experimental features enriched among biologically impactful fusions. Through clustering and machine learning, we identified large collections of fusions potentially relevant to tumor and normal biological processes. We show that biologically relevant fusions are enriched for relatively high expression of the fusion transcript, imbalanced fusion allelic ratios, and canonical splicing patterns, and are deficient in sequence microhomologies between partner genes. We demonstrate that FusionInspector accurately validates fusion transcripts in silico and helps characterize numerous understudied fusions in tumor and normal tissue samples. FusionInspector is freely available as open source for screening, characterization, and visualization of candidate fusions via RNA-seq, and facilitates transparent explanation and interpretation of machine-learning predictions and their experimental sources.

The Interplay between T Cells and Cancer: The Basis of Immunotherapy

Over the past decade, immunotherapy has emerged as one of the most promising approaches to cancer treatment. The use of immune checkpoint inhibitors has resulted in impressive and durable clinical responses in the treatment of various cancers. Additionally, immunotherapy utilizing chimeric antigen receptor (CAR)-engineered T cells has produced robust responses in blood cancers, and T cell receptor (TCR)-engineered T cells are showing promising results in the treatment of solid cancers. Despite these noteworthy advancements in cancer immunotherapy, numerous challenges remain. Some patient populations are unresponsive to immune checkpoint inhibitor therapy, and CAR T cell therapy has yet to show efficacy against solid cancers. In this review, we first discuss the significant role that T cells play in the body's defense against cancer. We then delve into the mechanisms behind the current challenges facing immunotherapy, starting with T cell exhaustion due to immune checkpoint upregulation and changes in the transcriptional and epigenetic landscapes of dysfunctional T cells. We then discuss cancer-cell-intrinsic characteristics, including molecular alterations in cancer cells and the immunosuppressive nature of the tumor microenvironment (TME), which collectively facilitate tumor cell proliferation, survival, metastasis, and immune evasion. Finally, we examine recent advancements in cancer immunotherapy, with a specific emphasis on T-cell-based treatments.

ALAN is a computational approach that interprets genomic findings in the context of tumor ecosystems

Gene behavior is governed by activity of other genes in an ecosystem as well as context-specific cues including cell type, microenvironment, and prior exposure to therapy. Here, we developed the Algorithm for Linking Activity Networks (ALAN) to compare gene behavior purely based on patient -omic data. The types of gene behaviors identifiable by ALAN include co-regulators of a signaling pathway, protein-protein interactions, or any set of genes that function similarly. ALAN identified direct protein-protein interactions in prostate cancer (AR, HOXB13, and FOXA1). We found differential and complex ALAN networks associated with the proto-oncogene MYC as prostate tumors develop and become metastatic, between different cancer types, and within cancer subtypes. We discovered that resistant genes in prostate cancer shared an ALAN ecosystem and activated similar oncogenic signaling pathways. Altogether, ALAN represents an informatics approach for developing gene signatures, identifying gene targets, and interpreting mechanisms of progression or therapy resistance.

Aptamers against cancer drug resistance: Small fighters switching tactics in the face of defeat

Discovering novel cancer therapies has attracted extreme interest in the last decade. In this regard, multidrug resistance (MDR) to chemotherapies is the primary challenge in cancer treatment. Cancerous cells are growingly become resistant to existing chemotherapeutics by employing diverse mechanisms, highlighting the significance of discovering approaches to overcome MDR. One promising strategy is utilizing aptamers as unique tools to target elements or signalings incorporated in resistance mechanisms or develop active targeted drug delivery systems or chimeras enabling the precise delivery of novel agents to inhibit the conventionally undruggable resistance elements. Further, due to their advantages over their proteinaceous counterparts, particularly antibodies, including improved targeting action, enhanced thermal stability, easier production, and superior tumor penetration, aptamers are emerging and have frequently been considered for developing cancer therapeutics. Here, we highlighted significant chemoresistance pathways and thoroughly discussed using aptamers as prospective tools to surmount cancer MDR.

The Bone Marrow Immune Microenvironment in CML: Treatment Responses, Treatment-Free Remission, and Therapeutic Vulnerabilities

PURPOSE OF REVIEW

Tyrosine kinase inhibitors (TKIs) are very successful for the treatment of chronic myeloid leukaemia (CML) but are not curative in most patients due to persistence of TKI-resistant leukaemia stem cells (LSCs). The bone marrow immune microenvironment (BME) provides protection to the LSC through multidimensional interactions, driving therapy resistance, and highlighting the need to circumvent these protective niches therapeutically. This review updates the evidence for interactions between CML cells and the immune microenvironment with a view to identifying targetable therapeutic vulnerabilities and describes what is known about the role of immune regulation in treatment-free remission (TFR).

RECENT FINDINGS

Intracellular signalling downstream of the chemotactic CXCL12-CXCR4 axis, responsible for disrupted homing in CML, has been elucidated in LSCs, highlighting novel therapeutic opportunities. In addition, LSCs expressing CXCL12-cleaving surface protein CD26 were highly correlated with CML burden, building on existing evidence. Newer findings implicate the adhesion molecule CD44 in TKI resistance, while JAK/STAT-mediated resistance to TKIs may occur downstream of extrinsic signalling in the BME. Exosomal BME-LSC cross-communication has also been explored. Finally, further detail on the phenotypes of natural killer (NK) cells putatively involved in maintaining successful TFR has been published, and NK-based immunotherapies are discussed. Recent studies highlight and build on our understanding of the BME in CML persistence and TKI resistance, pinpointing therapeutically vulnerable interactions. Repurposing existing drugs and/or the development of novel inhibitors targeting these relationships may help to overcome these issues in TKI-resistant CML and be used as adjuvant therapy for sustained TFR.

PROTAC'ing oncoproteins: targeted protein degradation for cancer therapy

Molecularly targeted cancer therapies substantially improve patient outcomes, although the durability of their effectiveness can be limited. Resistance to these therapies is often related to adaptive changes in the target oncoprotein which reduce binding affinity. The arsenal of targeted cancer therapies, moreover, lacks coverage of several notorious oncoproteins with challenging features for inhibitor development. Degraders are a relatively new therapeutic modality which deplete the target protein by hijacking the cellular protein destruction machinery. Degraders offer several advantages for cancer therapy including resiliency to acquired mutations in the target protein, enhanced selectivity, lower dosing requirements, and the potential to abrogate oncogenic transcription factors and scaffolding proteins. Herein, we review the development of proteolysis targeting chimeras (PROTACs) for selected cancer therapy targets and their reported biological activities. The medicinal chemistry of PROTAC design has been a challenging area of active research, but the recent advances in the field will usher in an era of rational degrader design.

miR-495-3p sensitizes BCR-ABL1-expressing leukemic cells to tyrosine kinase inhibitors by targeting multidrug resistance 1 gene in T315I mutated cells

Chronic myeloid leukemia (CML) is a clonal hematopoietic malignancy driven by the BCR-ABL1 fusion oncoprotein. The development of tyrosine kinase inhibitors (TKIs) has deeply increased long-term survival of CML patients. Nonetheless, one patient out of four will switch TKI off owing either to drug intolerance or resistance partly due to amplification or mutations of BCR-ABL1 oncogene and alteration in ATP-binding cassette (ABC) transporters. Increasing evidence suggests the involvement of the microRNA miR-495-3p in cancer-associated chemoresistance through multidrug resistance 1 (MDR1) gene, which encodes an ATP-dependent efflux pump. Our study aimed at investigating the potential role of miR-495-3p in CML TKI chemo-sensitivity and determining the underlying molecular circuitry involved. We first observed that miR-495-3p expression was lower in BCR-ABL1-expressing cellular models in vitro. Notably, loss-of-function experiments showed increased proliferation associated with a decreased number of nondividing cells (G0/G1) and resistance to Imatinib. Conversely, our data showed that miR-495-3p overexpression hindered leukemic cell growth and TKI resistance in Imatinib-resistant T315I-mutant cells, as well as drug efflux activity through MDR1 regulation. Further investigating the role of miR-495-3p in CML patients, we found that predicted miR-495-3p targets were upregulated in patients in blast crisis that were involved in protein phosphorylation and associated with the worst prognosis. Taken together, our results demonstrate that downregulation of miR-495-3p expression is important in the malignant phenotype of CML and TKI resistance mechanisms and could be a useful biomarker and a potential therapeutic target to eradicate CML.

Recent progress in the management of pediatric chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a rare myeloproliferative disease in children. The primary cause of CML is the chimeric BCR::ABL1 gene in hematopoietic stem cells, which leads to leukocytosis, platelet proliferation, and splenomegaly. Lately, tyrosine kinase inhibitors (TKIs) have replaced hematopoietic cell transplantation, which was previously considered the only curative therapy, as the first-line treatment for chronic-phase CML. However, the clinical efficacy of TKIs, including those effective in adult CML, has not been well-investigated in pediatric CML. This review describes the recommended TKI-based management strategies for pediatric CML according to the literature and guidelines. Furthermore, we discuss the prospects for TKI discontinuation to avoid important adverse events, such as growth impairment, in children.

Piperlongumine overcomes imatinib resistance by inducing proteasome inhibition in chronic myelogenous leukemia cells

ETHNOPHARMACOLOGICAL RELEVANCE

Piper longum L., an herbal medicine used in India and other Asian countries, is prescribed routinely for a range of diseases, including tumor. Piperlongumine, a natural product isolated from Piper longum L., has received widespread attention due to its various pharmacological activities, such as anti-inflammatory, antimicrobial, and antitumor effects.

AIM OF THE STUDY

Chronic myelogenous leukemia (CML) is a hematopoietic disease caused by Bcr-Abl fusion gene, with an incidence of 15% in adult leukemias. Targeting Bcr-Abl by imatinib provides a successful treatment approach for CML. However, imatinib resistance is an inevitable issue for CML treatment. In particular, T315I mutant is the most stubborn of the Bcr-Abl point mutants associated with imatinib resistance. Therefore, it is urgent to find an alternative approach to conquer imatinib resistance. This study investigated the role of a natural product piperlongumine in overcoming imatinib resistance in CML.

MATERIALS AND METHODS

Cell viability and apoptosis were evaluated by MTS assay and Annexin V/propidium iodide counterstaining assay, respectively. Levels of intracellular signaling proteins were assessed by Western blots. Mitochondrial membrane potential was reflected by the fluorescence intensity of rhodamine-123. The function of proteasome was detected using 20S proteasomal activity assay, proteasomal deubiquitinase activity assay, and deubiquitinase active-site-directed labeling. The antitumor effects of piperlongumine were assessed with mice xenografts.

RESULTS

We demonstrate that (i) Piperlongumine inhibits proteasome function by targeting 20S proteasomal peptidases and 19S proteasomal deubiquitinases (USP14 and UCHL5) in Bcr-Abl-WT and Bcr-Abl-T315I CML cells; (ii) Piperlongumine inhibits the cell viability of CML cell lines and primary CML cells; (iii) Proteasome inhibition by piperlongumine leads to cell apoptosis and downregulation of Bcr-Abl; (iv) Piperlongumine suppresses the tumor growth of CML xenografts.

CONCLUSIONS

These results support that blockade of proteasome activity by piperlongumine provides a new therapeutic strategy for treating imatinib-resistant CML.

Long-term stable disease with mFOLFOX6 chemotherapy plus cetuximab for bone marrow metastasis from rectal cancer: A case report

Bone marrow metastasis from rectal cancer is a rare but severe disease associated with a poor prognosis due to limited treatment options. There is no consensus on therapeutic strategies, and better-tolerated and more effective treatment options are urgently needed. We report a case that one patient with rectal cancer developed pancytopenia 15 months after completion of radical surgery and chemotherapy and was diagnosed with bone marrow metastasis. The patient was treated with mFOLFOX6 chemotherapy plus cetuximab, considering both his poor bone marrow function and a genetic test showing a wild-type of KRAS/NRAS/PIK3CA/BRAF. Twelve cycles were successfully completed with dose modifications and supportive measures. The patient's condition improved markedly based on a comprehensive assessment that included computed tomography images, blood cell counts, tumor markers, and clinical symptoms. The patient remains alive for 11 months at the last follow up. The patient treated with mFOLFOX6 chemotherapy plus cetuximab attained long-term stable disease, suggesting its promising efficacy and safety for bone marrow metastasis from rectal cancer and may hold promise as a treatment strategy for this specific patient population. Consideration can be given to the inclusion of mFOLFOX6 chemotherapy plus cetuximab in first-line treatment regimen for bone marrow metastasis from rectal cancer.

Progress of small molecules for targeted protein degradation: PROTACs and other technologies

Recent years have witnessed the rapid development of targeted protein degradation (TPD), especially proteolysis targeting chimeras. These degraders have manifested many advantages over small molecule inhibitors. To date, a huge number of degraders have been excavated against over 70 disease-related targets. In particular, degraders against estrogen receptor and androgen receptor have crowded into phase II clinical trial. TPD technologies largely expand the scope of druggable targets, and provide powerful tools for addressing intractable problems that can not be tackled by traditional small molecule inhibitors. In this review, we mainly focus on the structures and biological activities of small molecule degraders as well as the elucidation of mechanisms of emerging TPD technologies. We also propose the challenges that exist in the TPD field at present.

Functional antibody delivery: Advances in cellular manipulation

The current therapeutic antibody market in the U.S. consists of 100 antibody-based products and their market value is expected to explode beyond $300 billion by 2025. These therapies are presently limited to extracellular targets due to the innate inability of antibodies to transverse membranes. To expand the number of accessible therapeutic targets, intracellular antibody delivery is necessary. Many delivery vehicles for antibodies have been used with some promising results, such as nanoparticles and cell penetrating polymers. Despite the success of these delivery platforms using model antibody cargo, there is a surprisingly small number of studies that focus on functional antibody delivery into the cytosol that also measures a cellular response. Antibodies can be designed for essentially unlimited targets, including proteins and DNA, that will ultimately control cell function once delivered inside cells. Advancement in cellular manipulation depends on the application of intracellularly delivering functional antibodies to achieve a desired result. This review focuses on the emerging field of functional antibody delivery which enables various cellular responses and cell manipulation.

Synthesis and Biochemical Evaluation of Monocarboxylic GRB2 SH2 Domain Inhibitors

This protocol discloses the synthesis of monocarboxylic inhibitors with a macrocyclic peptide scaffold to bind with the GRB2 SH2 domain and disrupt the protein-protein interactions (PPIs) between GRB2 and phosphotyrosine-containing proteins.

Proteolysis-Targeting Chimeras (PROTACs) targeting the BCR-ABL for the treatment of chronic myeloid leukemia - a patent review

INTRODUCTION

PROteolysis-TArgeting Chimeras (PROTACs) allow the selective degradation of a protein of interest (POI) by the ubiquitin-proteasome system (UPS). With this unique mechanism of action, the research and development of PROTACs that target the Breakpoint Cluster Region Abelson (BCR-ABL) tyrosine kinase (TK) has been increasing dramatically, as they are promising molecules in the treatment of Chronic Myeloid Leukemia (CML), one of the main hematological malignancies, which results from an uncontrolled myeloproliferation due to the constitutive activation of BCR-ABL.

AREAS COVERED

This review summarizes the patents/applications published in the online databases like Espacenet or World Intellectual Property Organization regarding PROTACs that promote BCR-ABL degradation. Patents will be described mostly in terms of chemical structure, biochemical/pharmacological activities, and potential clinical applications.

EXPERT OPINION

The recent discovery of the enormous potential of PROTACs led to the creation of new compounds capable of degrading BCR-ABL for the treatment of CML. Although still in reduced numbers, and in the pre-clinical phase of development, some compounds have already been shown to overcome some of the difficulties presented by conventional BCR-ABL inhibitors, such as the well-known imatinib. Therefore, it is very likely that some of the present PROTACs will enter future CML therapy in the coming years.

Emerging roles of circRNAs in leukemia and the clinical prospects: An update

BACKGROUND

Circular RNAs (circRNAs) are a new category of endogenous non-protein coding RNAs (ncRNAs), and show the characteristics of high conservation, stability, and tissue specificity. Due to rapid advances in next-generation sequencing and transcriptome profiling technologies, circRNAs have been widely discovered in many organisms and participated in the development and progress of a variety of diseases. As a type of molecular sponge, circRNAs mainly absorb micro RNAs competitively and interplay with RNA-binding proteins to modulate the splicing as well as transcription of target genes.

METHODS

This review is based on a literature search using the Medline database. Search terms used were "circular RNAs and leukemia," "circRNAs and leukemia," "circRNAs and acute lymphoblastic leukemia," "circRNAs and chronic lymphoblastic leukemia," "circRNAs and acute myeloid leukemia," "circRNAs and chronic myeloid leukemia," and "circRNAs, biomarker, and hematological system."

RESULTS

CircRNAs have been proven as potential biomarkers and therapeutic targets in a variety of tumors. Recent research has found that circRNAs aberrantly exist in hematological cancers, especially leukemia, and are significantly associated with the incidence, progress, and metastasis of diseases as well as the prognosis of patients.

CONCLUSION

The current work summarizes the latest findings on circRNAs in various types of leukemia, aiming to propose prospective therapies and new drug screening methods for the treatment of leukemia.

Higher-order interactions of Bcr-Abl can broaden chronic myeloid leukemia (CML) drug repertoire

Bcr-Abl, a nonreceptor tyrosine kinase, is associated with leukemias, especially chronic myeloid leukemia (CML). Deletion of Abl's N-terminal region, to which myristoyl is linked, renders the Bcr-Abl fusion oncoprotein constitutively active. The substitution of Abl's N-terminal region by Bcr enables Bcr-Abl oligomerization. Oligomerization is critical: it promotes clustering on the membrane, which is essential for potent MAPK signaling and cell proliferation. Here we decipher the Bcr-Abl specific, step-by-step oligomerization process, identify a specific packing surface, determine exactly how the process is structured and identify its key elements. Bcr's coiled coil (CC) domain at the N-terminal controls Bcr-Abl oligomerization. Crystallography validated oligomerization via Bcr-Abl dimerization between two Bcr CC domains, with tetramerization via tight packing between two binary assemblies. However, the structural principles guiding Bcr CC domain oligomerization are unknown, hindering mechanistic understanding and drugs exploiting it. Using molecular dynamics (MD) simulations, we determine that the binary complex of the Bcr CC domain serves as a basic unit in the quaternary complex providing a specific surface for dimer-dimer packing and higher-order oligomerization. We discover that the small α1-helix is the key. In the binary assembly, the helix forms interchain aromatic dimeric packing, and in the quaternary assembly, it contributes to the specific dimer-dimer packing. Our mechanism is supported by the experimental literature. It offers the key elements controlling this process which can expand the drug discovery strategy, including by Bcr CC-derived peptides, and candidate residues for small covalent drugs, toward quenching oligomerization, supplementing competitive and allosteric tyrosine kinase inhibitors.

Wee1 promotes cell proliferation and imatinib resistance in chronic myeloid leukemia via regulating DNA damage repair dependent on ATM-γH2AX-MDC1

BACKGROUND

The treatment of chronic myeloid leukemia (CML) is facing the dilemma of tyrosine kinase inhibitors (TKIs) resistance and disease recurrence. The dysfunctional DNA damage repair mechanism plays an essential role not only in the initiation and progression of hematological malignancies but also links to the development of TKI resistance. Deciphering the abnormally regulated DNA damage repair and proteins involved brings new insights into the therapy of leukemias. As a G2/M phase checkpoint kinase and a DNA damage repair checkpoint kinase engaged in the DNA damage response (DDR), along with an oncogenic driver present in various cancers, the particular involvement of Wee1 in DNA damage is far from clear. Deciphering its function and targeting it via modulating DNA repair pathways is important for improving our understanding of cancer treatment.

METHODS

Wee1 expression was assessed in cell lines using RT-qPCR and western blot, and Wee1 knockdown efficacy was validated using RT-qPCR, western blot, and immunofluorescence. Wee1 function was investigated by CCK-8, colony formation, and flow cytometry assay in vitro. Wee1 role in DNA repair and its interactions with other proteins were then studied using western blot, immunofluorescence, and double plasmid-repair studies. Finally, the CCK-8 and flow cytometry assay was utilized to investigate Wee1 and imatinib's synergistic effect, and a CML mouse model was constructed to study Wee1's role in carcinogenesis in vivo.

RESULTS

Wee1 was reported to respond quickly to DDR in an ATM-γH2AX-MDC1-dependent way upon DNA double-strand breaks (DSBs) occurrence, and it regulated homologous recombination by stimulating the recruitment of critical proteins RAD51/BRCA1 upon DSB sites. Wee1 was also revealed to be abnormally upregulated in CML cells. Further suppression of Wee1 not only causes cell cycle arrest and inhibits the proliferation of cancer cells but also enhances CML cell sensitivity to Imatinib in vitro and in vivo, possibly through an excessive accumulation of overall DSBs.

CONCLUSION

Wee1 is extensively involved in the DRR signaling and DSB repair pathway. Inhibiting abnormally elevated Wee1 benefits CML therapy in both IM-resistant and IM-sensitive cells. Our data demonstrated that Wee1 participated in promoting cell proliferation and imatinib resistance in chronic myeloid leukemia via regulating DNA damage repair dependent on ATM-γH2AX-MDC1. In the fight against CML, Wee1's dysregulation in the DNA damage repair mechanism of CML pathogenesis makes it a viable therapeutic target in clinical applications.

SH2 Domains: Folding, Binding and Therapeutical Approaches

SH2 (Src Homology 2) domains are among the best characterized and most studied protein-protein interaction (PPIs) modules able to bind and recognize sequences presenting a phosphorylated tyrosine. This post-translational modification is a key regulator of a plethora of physiological and molecular pathways in the eukaryotic cell, so SH2 domains possess a fundamental role in cell signaling. Consequently, several pathologies arise from the dysregulation of such SH2-domains mediated PPIs. In this review, we recapitulate the current knowledge about the structural, folding stability, and binding properties of SH2 domains and their roles in molecular pathways and pathogenesis. Moreover, we focus attention on the different strategies employed to modulate/inhibit SH2 domains binding. Altogether, the information gathered points to evidence that pharmacological interest in SH2 domains is highly strategic to developing new therapeutics. Moreover, a deeper understanding of the molecular determinants of the thermodynamic stability as well as of the binding properties of SH2 domains appears to be fundamental in order to improve the possibility of preventing their dysregulated interactions.